Alpha-adrenoreceptor influences on liquid movements by in vitro lungs from fetal guinea pigs.
Lungs from near-term fetal guinea pigs (60 +/- 2 days of gestation) were supported in vitro for 3 h; lung liquid production was monitored by a dye-dilution method. Studies of 30 fetuses showed that untreated preparations produced fluid at 1.34 +/- 0.21 ml.h-1.kg body wt-1, but epinephrine at concentrations known at delivery (10(-8) and 10(-7) M) produced significant reductions or fluid reabsorption (analysis of variance, regression analysis); at high levels (10(-6) and 10(-5) M, epinephrine had no effect. Maximal responses from 10(-7) M epinephrine involved alpha-adrenoreceptors, since they were abolished by 10(-6) M phentolamine (alpha-antagonist) but were unaffected by 10(-6) M propranolol (beta-antagonist; n = 36). Activation was through alpha2-adrenoreceptors, since responses were abolished by 10(-4) M yohimbine (alpha-antagonist; n = 24) but were resistant to 10(-5) M prazosin (alpha 1-antagonist; n = 24). At high levels of epinephrine (10(-5) M), where responses did not normally occur, reductions in lung liquid production were large if prazosin was also present (n = 24), and increases were significant if yohimbine was included (n = 24). In guinea pigs, epinephrine appears to activate lung fluid reabsorption through alpha 2-adrenoreceptors; at high concentrations only, it can also increase production through alpha 1-adrenoreceptors. Therefore, species differences appear to exist.
Doe
S
S
Department of Obstetrics and Gynecology, University of British Columbia, Vancouver, Canada.
Perks
A M
AM
D058668:Adrenergic alpha-1 Receptor Antagonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001826:Body Fluids / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000494:pharmacology / Q000502:physiology; D005333:Fetus / Q000502:physiology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects / Q000196:embryology / Q000502:physiology*; D011224:Prazosin / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
D058668:Adrenergic alpha-1 Receptor Antagonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D011224:Prazosin; D004837:Epinephrine